Electroplating chromium with a nonconsumable chrome plating anode

ABSTRACT

A NON-CONSUMABLE CHROME PLATING ANODE WHICH IS AN ANODE SHAPED LEAD BODY, WITH NOT LESS THAN 20 P.P.M. CALCIUM AND UP TO APPROXIMATELY 3% TIN ALLOYED WITH THE LEAD.

United States Patent ELECTROPLATING CHROMIUM WITH A NON- CONSUMABLECHROME PLATING ANODE Howard Manko, Teaneck, and James Langan, Bayonne,

N.J., assiguors to Alpha Metals, Inc.,.Huds'on County,

No Drawing. Filed Aug. 11, 1972, Ser. No. 279,947 Int. Cl. C23b 5/ 06US. Cl. 204-51 I 4 Claims ABSTRACT OF THE DISCLOSURE A non-consumablechrome plating anode which is an anode shaped lead body, with not lessthan 20 p.p.m. calcium and up to approximately 3% tin alloyed with thelead.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates generally to non-consumable chrome plating anodes andparticularly to such anodes which are highly resistant to deformation inshape under varying conditions of temperature operation, and have thefurther characteristic of forming thereon a benevolent, adherent scale,said scale contributing substantially to the extended life of the anode.

Description of the prior art Numerous anodes are available forelectroplating of chrome. It is frequently found that heat requiredduring the electrodeposition process causes a physical deformation ofthe anode, which initially may move portions of the anode away from thework piece, thereby retarding the rate of deposition, and move otherportions of the anode toward the work piece, thereby accelerating therate of electrodeposition. The net result is an uneven rate ofelectrodeposition, in many instances of highly unsatisfactory characterrequiring the rejection of the plated work piece. Further deformation ofthe electrode may actually bring it into physical contact with the workpiece, shorting the circuit with catastrophic results. Conventionalanodes frequently accumulate scale which is of such a character that itimpairs the process of electrodeposition. The character and quality ofsuch scale is well-known to those who practice the art of chromeplating. During down time, the electrodes are usually removed from thebath for the purpose of removal of scale. If it is not removed, thescale may deteriorate, or it may be necessary to de-plate it. It becomesapparent that an ideal chrome plating anode would be one which would notdeform, would not be subject to deleterious scaling during down time,and would have a vastly extended life.

SUMMARY OF THE INVENTION It has been found that a chrome plating anodecould be devised which has many of the desirable characteristics in avery high degree. This anode is composed principally of relatively highpurity lead containing not less than 20 p.p.m. calcium. The lead ispreferably alloyed with ap proximately /2 to 7% of high purity tin. Thepresence of the tin has a marked effect upon the scale formation on theanode. In the total absence of tin, the full potential of the anode isnot reached. The scale formed is thin, less adherent and the lead bodyis more rapidly consumed during the course of the electrodepositionprocess. On the other hand, even without the tin, the anodes with thefractional presence of calcium is a considerable improvement over theconventional chrome plating anode. However, with the addition of the tinin 3,794,570 Patented Feb. 26, 1974 the preferred range referred to, abenevolent scale is formed on the anode which does not interfere withthe rate of electrodeposition to any substantial degree, the scale isintimately adherent and is not readily discharged and forms a highlyprotective shield for the anode which vastly extends its useful lifeover what may be expected from a conventional anode. The character andquality of. the scale is not such as to cause an extensive heat build upin the body of the anode and the alloy of tin and lead is stabledimensionally due to the presence of the calcium so that deformation isnot a problem.

PREFERRED EMBODIMENTS A typical chrome plating anode as used in industryis two inches in diameter and may vary from six inches (used for chromeplating the interior of internal combustion engines and cylinders toimpart hardness) to twenty two feet (used for plating of decorativestructural parts). Intermediate of these extremes would be a six footanode two inches in diameter used for chrome plating of automobilebumpers. The anode may be prepared by either casting, extruding,rolling, drawings, extending, forming, cladding or any other suitablemanner.

The anode is prepared by any of the above well-known methods. The anoderequires no particular chrome plating bath to function (excepting,however, chloride base electrolyte baths) and any of the well knownelectrolytes 1n current use for chrome plating will functionsatisfactorily. No additives are required to enhance the platingoperation or the brightness, because of the special qualities of theanode. The price of the anode presents a great economy due to its vastlyextended life and low cost composition, for it may be expected to serveunder ordinary circumstances for periods of up to ten years. The platingproduced has a high degree of uniformity, free of burns and visiblesurface imperfections commonly referred to as treeing. The choice ofappropriate current density and the concentration of materials in theelectrolyte, the presence of additives are all matters which are wellknown to those skilled in the art and need not be varied to suit thepresent electrode.

What is claimed is:

1. The method of chrome plating with a non-consumable plating anodesubjected to scale formation and temperature variation during a chromeplating operation comprising:

(a) preparing a plating anode consisting essentially of 20 p.p.m.calcium and the remainder lead, and

(b) electrodepositing chrome on a workpiece with the anode.

2. The method of chrome plating with a non-consumable plating anodesubjected to scale formation and temperature variation during a chromeplating operation comprising:

(a) preparing a plating anode consisting essentially of 20 p.p.m.calcium, about .57% tin and the remainder lead, and

(b) electrodepositing chrome on a workpiece yvith t1 1e V anode.

3. The method of chrome plating with a non-consumable plating anodesubjected to scale formation and temperature variation during a chromeplating operating comprising: g

(a) preparing a plating anode consisting essentially of 20 p.p.m.calcium, about 25-35% silver, and the remainder lead, and

(b) electrodepositing chrome on a workpiece with the anode.

4. The method of chrome plating with a nonconsumable plating anodesubjected to scale formation and temperature variation during a chromeplating operating comprising:

20 p.p.m. calcium, about .57.0% tin, about .25-

3.5% silver, and

the remainder lead, and

(b) electrodepositing chrome on a workpiece with the References CitedUNITED STATES PATENTS Betterton et a1 75167 Shoemaker 75167 Eldridge204-293 X FOREIGN PATENTS 5 anode.

Germany 204--293 US. Cl. X.R.

